1. Field of the Invention
The invention relates to a vacuum cleaning tool for a vacuum cleaning device, comprising a housing with a turbine chamber in which an air turbine is arranged that is rotatably driven by a suction airflow of the vacuum cleaning device about an axis of rotation. The air turbine drives a cleaning tool that is rotatably supported in a working chamber of the housing, wherein the bottom plate of the housing has a suction slot extending transversely to the working direction of the vacuum cleaning tool. The suction airflow enters the working chamber via the suction slot. A flow connection is provided between the working chamber and the turbine chamber, and the suction airflow for driving the air turbine enters the turbine chamber via the flow connection. An outlet opening is provided allowing the suction airflow to exit the turbine chamber.
2. Description of the Related Art
Such a vacuum cleaning device is described in EP 0 338 780 A2. For adjusting the drive power, a slide is provided which guides the suction airflow completely or partially toward the air turbine. For lowering the drive power, the slide must be moved horizontally in order to guide a portion of the suction airflow past one axial end of the air turbine. The resulting configuration of the turbine chamber impairs an optimal adjustment of the drive for obtaining a maximum efficiency of the suction airflow. Even when the air turbine is loaded with the entire suction airflow, a satisfactory drive power cannot be obtained.
It is an object of the present invention to configure a vacuum cleaning tool of the aforementioned kind such that for a high power yield a powerful drive of the cleaning tool can be obtained even under unfavorable working conditions while, at the same time, a simple adjustability of the air turbine output is possible.
In accordance with the present invention, this is achieved in that a second flow connection is provided between the working chamber and the turbine chamber, in that the first flow connection is located on one side of an imaginary plane and the second flow connection on the other side of the imaginary plane, wherein the plane is defined by the axis of rotation of the air turbine and the center of the outlet opening, and wherein the cross-section of one of the flow connections is adjustable.
According to the invention, in addition to the first flow connection between the working chamber and the turbine chamber provided for the driving airflow, a second flow connection is provided between these two chambers so that the suction airflow entering the working chamber through the suction slot can be divided into two partial flows. This has the advantage that the entire power of the suction airflow is always available at the suction slot for enabling a high cleaning action.
Since the first flow connection is positioned on one side of the plane, extending through the axis of rotation of the air turbine and the center of the outlet opening, and the second flow connection is positioned on the opposite side of this plane, a braking effect of the partial airflow entering the turbine chamber via the second flow connection results. This partial flow of the suction airflow loads the annular vane arrangement of the air turbine counter to its rotational direction so that not only the volume of the driving suction airflow of the first flow connection is reduced but, moreover, the branched-off partial airflow is used for braking. Accordingly, already a small partial airflow can result in a significant rotational speed decrease with reduced power output. The cross-sectional surface area of the flow connection for the braking airflow can therefore be smaller than the flow connection of the driving airflow. In this way, an arrangement of the two windows of the flow connections atop one another is possible in the partition between the working chamber and the turbine chamber.
Preferably, the cross-section of the second flow connection is adjustable while the cross-section of the first flow connection cannot be changed and is fixed. The second flow connection comprises an adjustable closure which is formed as a slide, preferably as a rotary slide. In this way, the flow connection for the braking airflow can have the cross-section of a semi-circle and the closure can be configured as a full circle (circular) disk in which an inner, preferably semi-circular, cutout, matching the cross-section of the flow connection, is provided for the braking airflow.
The closure in the form of a disk can be manually adjusted for which purpose the circumferential edge of the disk projects with a portion thereof from the housing through a slot provided in the housing. Expediently, the circumferential edge of the disk is knurled.